This invention relates to a fuel system for use in supplying fuel under high pressure to a combustion space of an internal combustion engine. In particular, the invention relates to a fuel system of the type in which the timing of fuel delivery is controlled using a control fluid independent of the fuel to be delivered.
Such a fuel system is suitable for use with engines used in certain marine applications in which the fuel is of relatively high viscosity at low temperatures and so is not suitable for lubricating the movement of valves, is unsuitable for use in controlling the operation of a fluid pressure actuable valve and may impede the operation of electromagnetic actuators used in controlling the operation of valves.
According to the present invention there is provided a fuel system of the type defined hereinbefore comprising a source of fuel arranged to be charged with fuel to a high pressure, a fluid pressure actuable valve controlling communication between the fuel source and an injection nozzle, a source of control fluid under pressure, and a control valve controlling the application of control fluid under pressure to the fluid pressure actuable valve to control operation of the fluid pressure actuable valve.
The control valve is conveniently electromagnetic controlled and is conveniently located between the source of control fluid under pressure and the fluid pressure actuable valve. Alternatively, the control valve may be located between the fluid pressure actuable valve and a low pressure drain. In either case, the control valve is conveniently arranged to control the fluid pressure within a control chamber defined, in part, by a surface associated with the fluid pressure actuable valve.
The fluid pressure actuable valve is conveniently further arranged to control communication between at least one passage and/or chamber of the injection nozzle and a low pressure fuel reservoir.
The injection nozzle, the fluid pressure actuable valve and the control valve conveniently form part of a fuel injector. The invention also relates to such a fuel injector.